Fin isolation structure for finfet and method of forming the same

ABSTRACT

A semiconductor device structure is provided. The semiconductor device structure includes a substrate having adjacent first and second fins protruding from the substrate, an isolation feature between and adjacent to the first fin and the second fin, and a fin isolation structure between the first fin and the second fin. The fin isolation structure includes a first insulating layer partially embedded in the isolation feature, a second insulating layer having sidewall surfaces and a bottom surface that are covered by the first insulating layer, a first capping layer covering the second insulating layer and having sidewall surfaces that are covered by the first insulating layer, and a second capping layer having sidewall surfaces and a bottom surface that are covered by the first capping layer.

PRIORITY CLAIM AND CROSS-REFERENCE

This Application claims the benefit of U.S. Provisional Application No. 62/732,657, filed on Sep. 18, 2018, and entitled “FIN ISOLATION STRUCTURE FOR FINFET AND METHOD OF FORMING THE SAME,” the entirety of which is incorporated by reference herein.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. As the semiconductor industry has progressed into nanometer technology process nodes in pursuit of higher device density, higher performance, and lower costs, challenges from both fabrication and design issues have resulted in the development of three-dimensional designs, such as the fin field effect transistor (FinFET). FinFETs are fabricated with a thin vertical “fin” (or fin structure) extending from a substrate. The channel of the FinFET is formed in this vertical fin. A gate is provided over three sides (e.g., wrapping) the fin. Advantages of the FinFET may include reducing the short channel effect and increasing the current flow.

Although existing FinFET manufacturing processes have been generally adequate for their intended purposes, as the size of FinFET scaling-down continues, they have not been entirely satisfactory in formation of isolation structure for adjacent fins in the FinFET device structure.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It should be noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIGS. 1, 2, 3, 4, 5, 6, 7, 8, and 9 show perspective representations of various stages of forming a semiconductor device structure, in accordance with some embodiments of the disclosure.

FIG. 10 is a schematic cross-sectional view showing the semiconductor device structure taken along the line 10-10′ in FIG. 9.

FIGS. 11, 12, and 13 show perspective representations of various stages of forming a semiconductor device structure, in accordance with some embodiments of the disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, or examples, for implementing different features of the subject matter provided. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows includes embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. The present disclosure may repeat reference numerals and/or letters in some various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between some various embodiments and/or configurations discussed.

Furthermore, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

Some embodiments of the disclosure are described. Additional operations can be provided before, during, and/or after the stages described in these embodiments. Some of the stages that are described can be replaced or eliminated for different embodiments. Additional features can be added to the semiconductor device structure. Some of the features described below can be replaced or eliminated for different embodiments. Although some embodiments are discussed with operations performed in a particular order, these operations may be performed in another logical order.

Embodiments of the disclosure form a semiconductor device structure with FinFETs. The fins may be patterned using any suitable method. For example, the fins may be patterned using one or more photolithography processes, including double-patterning or multi-patterning processes. Generally, double-patterning or multi-patterning processes combine photolithography and self-aligned processes, allowing patterns to be created that have, for example, pitches smaller than what is otherwise obtainable using a single, direct photolithography process. For example, in one embodiment, a sacrificial layer is formed over a substrate and patterned using a photolithography process. Spacers are formed alongside the patterned sacrificial layer using a self-alignment process. The sacrificial layer is then removed, and the remaining spacers may then be used to pattern the fins.

Embodiments of methods of forming a semiconductor device structure are provided. The formation of the semiconductor device structure includes forming an insulating liner over a substrate having at least adjacent two fins. Afterwards, a first insulating layer is formed over the insulating liner to cover the adjacent fins and the substrate between the adjacent fins. Afterwards, a second insulating layer is formed over the first insulating layer between the adjacent fins, and a first capping layer and a second capping layer are successively formed over the first insulating layer and the second insulating layer. Afterwards, a chemical mechanical polishing (CMP) process is performed to expose the adjacent fins and form a dual capping structure that includes the remaining first and second capping layers over the second insulating layer. This remaining second capping layer is made of a nitrogen-free material and serves as a CMP stop layer for exposure of the first and second fins. As a result, the nitrogen-free material prevents the property of the CMP slurry from being changed, so as to ensure that the CMP process can stop on the top surfaces of the first and second fins.

FIGS. 1, 2, 3, 4, 5, 6, 7, 8, and 9 show perspective representations of various stages of forming a semiconductor device structure, in accordance with some embodiments of the disclosure. In some embodiments, the semiconductor device structure is implemented as a fin field effect transistor (FinFET) structure. As shown in FIG. 1, a substrate 100 is provided. In some embodiments, the substrate 100 is a semiconductor substrate, such as a bulk semiconductor, a semiconductor-on-insulator (SOI) substrate, or the like, which may be doped (e.g. with a P-type or an N-type dopant) or undoped. In some embodiments, the substrate 100 is a wafer, such as a silicon wafer. Generally, an SOI substrate includes a layer of a semiconductor material formed on an insulator layer. The insulator layer may be, for example, a buried oxide (BOX) layer, a silicon oxide layer, or the like. The insulator layer is provided on a substrate, typically a silicon or glass substrate.

Other substrates, such as a multi-layered or gradient substrate may also be used. In some embodiments, the semiconductor material of the substrate 100 includes silicon; germanium; a compound semiconductor including silicon carbide, gallium arsenic, gallium phosphide, indium phosphide, indium arsenide, and/or indium antimonide; an alloy semiconductor including SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; or a combination thereof. In some embodiments, the substrate 100 includes silicon. In some embodiments, the substrate 100 includes an epitaxial layer. For example, the substrate 100 has an epitaxial layer overlying a bulk semiconductor.

In some embodiments, the substrate 100 has a PMOS region for P-type FinFETs formed thereon and/or an NMOS region for N-type FinFETs formed thereon. In some embodiments, the PMOS region of the substrate 100 includes Si, SiGe, SiGeB, or an III-V group semiconductor material (such as InSb, GaSb, or InGaSb). The NMOS region of the substrate 100 includes Si, SiP, SiC, SiPC, or an III-V group semiconductor material (such as InP, GaAs, AlAs, InAs, InAlAs, or InGaAs).

Afterwards, the substrate 100 is patterned to form a fin structure 101 including fins and trench openings between adjacent fins, in accordance with some embodiments. In some embodiment, before the substrate 100 is patterned, a first masking layer 102 and a second masking layer 104 may be successively formed over the substrate 100. In some embodiments, the first masking layer 102 serves a buffer layer or an adhesion layer that is formed between the underlying substrate 100 and the overlying second masking layer 104. The first masking layer 102 may also be used as an etch stop layer when the second masking layer 104 is removed or etched. In some embodiments, the first masking layer 102 is made of silicon oxide. In some embodiments, the first masking layer 102 is formed by a deposition process, such as a chemical vapor deposition (CVD) process, a low-pressure chemical vapor deposition (LPCVD) process, a plasma enhanced chemical vapor deposition (PECVD) process, a high-density plasma chemical vapor deposition (HDPCVD) process, a spin-on process, or another applicable process.

In some embodiments, the second masking layer 104 is made of silicon oxide, silicon nitride, silicon oxynitride, or another applicable material. In some embodiments, the second masking layer 104 is formed by a deposition process, such as a chemical vapor deposition (CVD) process, a low-pressure chemical vapor deposition (LPCVD) process, a plasma enhanced chemical vapor deposition (PECVD) process, a high-density plasma chemical vapor deposition (HDPCVD) process, a spin-on process, or another applicable process.

After formation of the first masking layer 102 and the second masking layer 104, the first masking layer 102 and the overlying second masking layer 104 are patterned by a photolithography process and an etching process, so as to expose portions of the substrate 100. For example, the photolithography process may include photoresist coating (e.g., spin-on coating), soft baking, mask aligning, exposure, post-exposure baking, developing the photoresist, rinsing and drying (e.g., hard baking). Moreover, the etching process may be a dry etching process, such as a reactive ion etching (RIE) process, an neutral beam etching (NBE) process, the like, or a combination thereof.

Afterwards, an etching process is performed on the substrate 100 to form the fin structure 101 including fins protruding from the substrate 100 and trench openings in the substrate 100 by using the patterned first masking layer 102 and the patterned second masking layer 104 as an etch mask. In order to simplified the diagram, five fins 101 a, 101 b, 101 c, 101 d, and 101 e and four and trench openings 100 a, 100 b, 100 c, and 100 d are depicted as an example. In some embodiments, those fins 101 a, 101 b, 101 c, 101 d, and 101 e have different spaces therebetween. More specifically, the adjacent fins 101 a and 101 b that are spaced apart from each other by a distance D1 to define the trench opening 100 a. The adjacent fins 101 b and 101 c are spaced apart from each other by a distance D2 to define the trench opening 100 b. The adjacent fins 101 c and 101 d are spaced apart from each other by a distance D3 to define the trench opening 100 c. The adjacent fins 101 d and 101 e are spaced apart from each other by a distance D4 to define the trench opening 100 d. The distance D1 is greater than the distance D2, the distance D2 is greater than the distance D3, and the distance D3 is greater than the distance D4.

In some embodiments, the etching process for formation of the fin structure 101 is a dry etching process or a wet etching process. In an example, the substrate 100 is etched by a dry etching process, such as an RIE process, an NBE process, the like, or a combination thereof. The dry etching process may be performed using a process gas including fluorine-based etchant gas. For example, the process gas may include SF₆, C_(x)F_(y), NF₃ or a combination thereof. In some other embodiments, each of the fin structure 101 may have tapered sidewalls. For example, each of the fin structure 101 has a width that gradually increases from the top portion to the lower portion. A person of ordinary skill in the art will readily understand other methods of forming the fin structures, which are contemplated within the scope of some embodiments.

After the fin structure 101 is formed, an insulating liner 106 is formed over the patterned substrate 100, as shown in FIG. 1 in accordance with some embodiments. In some embodiments, the insulating liner 106 covers the surfaces of the patterned second masking layer 104, the patterned first masking layer 102, and the patterned substrate 100 having fins 101 a, 101 b, 101 c, 101 d, and 101 e. Since the distance D4 between the adjacent fins 101 d and 101 e is small, the insulating liner 106 may entirely fill the space between the adjacent fins 101 d and 101 e. Moreover, the insulating liner 106 conformally lines the sidewalls and bottoms of the other trench openings 100 a, 100 b, and 100 c.

In some embodiments, the insulating liner 106 is made of silicon oxide, fluorosilicate glass (FSG), a low-k dielectric material, and/or another suitable dielectric material or another low-k dielectric material. The insulating liner 106 may be deposited by an atomic layer deposition (ALD) process, a chemical vapor deposition (CVD) process, a flowable CVD (FCVD) process, or another applicable process.

After the insulating liner 106 is formed, a fin cut process is performed to divide each of the fins 101 a, 101 b, 101 c, 101 d, and 101 e into at least two parts, as shown in FIG. 2 in accordance with some embodiments. In some embodiments, after the fin cut process is performed, the fins 101 a, 101 b, 101 c, 101 d, and 101 e that are covered by the patterned first masking layer 102, the patterned second masking layer 194, and the insulating liner 106 are respectively separated into two parts so as to form a cutting opening 107 between the two parts of each fin. The fin cut process may include a photolithography process and an etching process (such as a wet etching process, a dry etching process, or a combination thereof).

After the fin cut process is performed, an insulating layer 110 is formed over the insulating liner 106, as shown in FIG. 3 in accordance with some embodiments. In some embodiments, the formed insulating layer 110 also covers the surfaces of the patterned second masking layer 104, the patterned first masking layer 102, and the patterned substrate 100 having fins 101 a, 101 b, 101 c, 101 d, and 101 e. Since the trench openings 100 b and 100 c (not shown and indicated in FIG. 1) become smaller after the formation of the insulating liner 106, the insulating layer may entirely fill the trench openings 106 b and 106 c. Moreover, the insulating layer 110 conformally lines the sidewalls and bottoms of the trench opening 100 a (not shown and indicated in FIG. 1) and the cutting opening 107 (not shown and indicated in FIG. 2) and respectively form an opening 110 a between the adjacent fins 101 a and 101 b and an opening 110 b between two parts of each fin. As a result, the insulating layer 110 in the trench opening 100 a is covered by the insulating liner 106.

In some embodiments, the insulating layer 110 is made of a nitrogen-containing material or carbon- and nitrogen-containing material. For example, the insulating layer 110 is made of SiN, SiON, SiCN, SiOCN, TiN, AlON or another applicable material. The insulating layer 110 may be deposited by an ALD process, a CVD process, or another applicable process.

After the insulating layer 110 is formed, the lower portions of the openings 110 a and 110 b are filled with an insulating layer 120, as shown in FIGS. 4 and 5 in accordance with some embodiments. In some embodiments, the insulating layer 120 is formed over the insulating layer 110 above the patterned second masking layer 104 and fills the openings 110 a and 110 b. As a result, the insulating layer 120 in the opening 110 a has sidewall surfaces 121 and a bottom surface 123 that are covered by the insulating layer 110, as shown in FIG. 4.

In some embodiments, the insulating layer 120 is made of a material that is the same as or similar to that of the insulating liner 106. For example, the insulating layer 12 is made of silicon oxide, FSG, a low-k dielectric material, and/or another suitable dielectric material or another low-k dielectric material. The insulating layer 12 may be formed by a deposition process, such as CVD, ALD, FCVD, high density plasma CVD (HDPCVD), metal organic CVD (MOCVD), plasma enhanced CVD (PECVD), or another applicable process.

Afterwards, a planarization layer (not shown) is form over the insulating layer 120 for subsequent planarization process, in accordance with some embodiments. In some embodiments, the planarization layer is made of a dielectric material, such as oxide, and is formed by a deposition process, such as CVD, PECVD, or another applicable process.

After the planarization layer is formed, a planarization process is performed on the planarization layer until the insulating layer 110 is exposed, as shown in FIG. 4 in accordance with some embodiments. In some embodiments, a CMP process is performed to remove the insulating layer 120 and the overlying planarization layer above the openings 1101 and 110 b to expose the insulating layer 110, so that the remaining insulating layer 120 has a top surface that is substantially level with that of the insulating layer 110.

In some embodiments, after the CMP process is performed, the remaining insulating layer 120 is further recessed by an etching process, such as a dry etching process, a wet etching process, or a combination thereof, as shown in FIG. 5. The insulating layer 120 is etched back to a depth to expose upper portions of the openings 110 a and 110 b, so that the top surface 120 a of the recessed insulating layer 120 is lower than the top surfaces 103 of the fins 101 a, 101 b, 101 c, 101 d, and 101 e. In some embodiments, the height difference between the top surface 120 a and the top surfaces 103 is in a range from about 1 Å to about 1000 Å.

After the insulating layer 120 is recessed to expose the upper portion of the openings 110 a and 110 b, a first capping layer 130 and a second capping layer 140 are successively formed over the structure shown in FIG. 5, as shown in FIG. 6 in accordance with some embodiments. In some embodiments, the first capping layer 130 is formed over the insulating layer 110 above the fins 101 a, 101 b, 101 c, 101 d, and 101 e and the insulating layer 120 in the openings 110 a and 110 b (not shown and indicated in FIG. 5) and conformally lines the upper portion of the openings 110 a and 110 b, so as to form openings 130 a and 130 b corresponding to the openings 110 a and 110 b and between the fins 101 a and 101 b and between the two parts of each fin.

In some embodiments, the first capping layer 130 in the opening 110 a has sidewall surfaces 131 covered by the insulating layer 110. Moreover, the second insulating layer 120 provides a sufficient recess depth, so that the bottom 133 of the opening 130 a is below the top surfaces 103 of the fins 101 a, 101 b, 101 c, 101 d, and 101 e. As a result, the top surfaces 103 of the fins 101 a, 101 b, 101 c, 101 d, and 101 e is higher than the bottom 133 of the opening 130 a and lower than the top surface of the subsequent formed second capping layer 140. In some embodiments, the first capping layer 130 serves as an etching stop layer for the subsequent etching process in the fabrication of the semiconductor device structure.

In some embodiments, the second capping layer 140 is formed over the insulating layer 110 above the patterned second masking layer 104 and fills the openings 130 a and 130 b. As a result, the second capping layer 140 in the opening 130 a has sidewall surfaces 131 and a bottom surface (i.e., the bottom 133 of the opening 130 a) that are covered by the first capping layer 130, so that the insulating layer 110 between the fins 101 a and 101 b is separated from the second capping layer 140 by the first capping layer 130.

In some embodiments, the first capping layer 130 is made of a nitrogen-containing material or carbon- and nitrogen-containing material. For example, the first capping layer 130 is made of SiN, SiON, SiCN, SiOCN, TiN, AlON or another applicable material. The first capping layer 130 may be deposited by an ALD process, a CVD process, or another applicable process. In some embodiments, the second capping layer 140 is made of a material that is different from the material of the first capping layer 130. For example, the second capping layer 140 is made of a nitrogen-free material. For example, the first second capping layer 140 is made of Si, SiC, SiOC, SiO, SiO₂, HfO_(x), ZrO₂, Al₂O₃, or another applicable material. The second capping layer 140 may be deposited by a CVD process, a PECVD process, or another applicable process.

After the second capping layer 140 is formed, a polishing process is performed on the structure shown in FIG. 6, as shown in FIG. 7 in accordance with some embodiments. In some embodiments, the layers above the fins 101 a, 101 b, 101 c, 101 d, and 101 e are removed by the polishing process, such as a CMP process, so as to expose the fins 101 a, 101 b, 101 c, 101 d, and 101 e and form a dual capping structure to cover the entire top surface 120 a (not shown and indicated in FIG. 5) of the insulating layer 120. More specifically, the second capping layer 140, the first capping layer 130, the insulating layer 110, the insulating liner 106, the patterned second masking layer 104, and the patterned first masking layer 102 above the fins 101 a, 101 b, 101 c, 101 d, and 101 e are successively removed by the polishing process, so that fins 101 a, 101 b, 101 c, 101 d, and 101 e are exposed. In some embodiments, the polishing process (e.g., the CMP process) is performed using a slurry including silicon suppressors and abrasive materials with an abrasive size in a range from about 1 nm to about 150 nm. The abrasive materials may include Ce(OH)_(x), CeO₂, SiO₂, TiO₂, Al₂O₃, ZrO₂, MnO, or the like or a combination thereof.

In some embodiments, the formed dual capping structure has a top surface that is substantially level with the top surface 103 of the fin structure 101 (i.e., the fins 101 a, 101 b, 101 c, 101 d, and 101 e). In those cases, the dual capping structure covering the insulating layer 120 includes a portion of the first capping layer 130 remaining in the opening 110 a (not shown and indicated in FIG. 5) and a portion of the second capping layer 140 remaining in the opening 130 a (not shown and indicated in FIG. 6). As a result, the first capping layer 130 is between the insulating layer 120 and the second capping layer 140, and the second capping layer 140 has a top surface that is substantially level with the top surface 103 of the fins 101 a, 101 b, 101 c, 101 d, and 101 e.

Although the first capping layer 130 made of a nitrogen-containing material can serve as an etching stop layer for the post etching process, the nitrogen atoms in the first capping layer 130 may react with the slurry to form ammonia or byproducts that is harmful of the silicon suppressors in the slurry and increases the pH value of the slurry. As a result, the remove rate of the fins 101 a, 101 b, 101 c, 101 d, and 101 e is increased due to the change of the property of the slurry, thereby undesirably reducing the fin height.

However, as shown in FIG. 7, when the fins 101 a, 101 b, 101 c, 101 d, and 101 e is exposed due to the polishing process, the contact area between the first capping layer 130 and the slurry is greatly reduced because the second capping layer 140 (which is made of a nitrogen-free material) covers the most of the top surface of the first capping layer 130. Accordingly, the second capping layer 140 greatly mitigates the reaction between the first capping layer 130 and the slurry, so as to prevent the property of the slurry from being changed.

Moreover, the polishing selectivity of the second capping layer 140 (which is made of a nitrogen-free material) to the fins 101 a, 101 b, 101 c, 101 d, and 101 e is greater than that of the first capping layer 130 (which is made of a nitrogen-containing material) to the fins 101 a, 101 b, 101 c, 101 d, and 101 e. Accordingly, the endpoint detection for the polishing process can be controlled by using the second capping layer 140 as a polishing stop layer, so that the polishing process can stop on the top surfaces 103 of the fins 101 a, 101 b, 101 c, 101 d, and 101 e. For example, the polishing selectivity of the second capping layer 140 to the fins 101 a, 101 b, 101 c, 101 d, and 101 e is more than 250 and the polishing selectivity of the first capping layer 130 to the fins 101 a, 101 b, 101 c, 101 d, and 101 e is more than 100.

As a result, since such a dual capping structure can ensure that the polishing process (e.g., the CMP process) is capable of stopping on the top surfaces 103 of the fins 101 a, 101 b, 101 c, 101 d, and 101 e, the fin loss problem can be mitigated or eliminated.

Afterwards, the remaining insulating liner 106 is further recessed, as shown in FIG. 8 in accordance with some embodiments. In some embodiments, a portion of the insulating liner 106 is removed by an etching process, so as to form an isolation feature 160 between and adjacent to the fins 101 a, 101 b, 101 c, 101 d, and 101 e. For example, the etching process may be a dry etching process, a wet etching process, or a combination thereof. The isolation feature 160 including the remaining insulating liner 106 may be shallow trench isolation (STI) structures that surround the fin structure 101. The lower portions of the fins 101 a, 101 b, 101 c, 101 d, and 101 e are surrounded by the isolation feature 160, and the upper portion of the fins 101 a, 101 b, 101 c, 101 d, and 101 e protrude from the isolation feature 160. In other words, a portion of the fin structure 101 is embedded in the isolation feature 160. The isolation feature 160 may prevent electrical interference or crosstalk.

In some embodiments, after the remaining insulating liner 106 is recessed, fin isolation structures 150 a, 150 b, and 150 c are also formed. The fin isolation structure 150 a is formed between the fins 101 a and 101 b, the fin isolation structure 150 b is formed between the fins 101 b and 101 c, and the fin isolation structure 150 c is formed between the fins 101 c and 101 d.

More specifically, the fin isolation structure 150 a includes the insulating layer 110 partially embedded in and surrounded by the isolation feature 160 between the fins 101 a and 101 b, the insulating layer 120 surrounded by the insulating layer 110, and the dual capping structure including the first capping layer 130 and the second capping layer 140 over the insulating layer 120 and surrounded by the insulating layer 110. The fin isolation structures 150 b includes the insulating layer 110 partially embedded in and surrounded by the isolation feature 160 between the fins 101 b and 101 c. Similarly, the fin isolation structures 150 c includes the insulating layer 110 partially embedded in and surrounded by the isolation feature 160 between the fins 101 c and 101 d.

After the isolation feature 160 and the fin isolation structures 150 a, 150 b, and 150 c are formed, dummy gate structures (not shown) are formed over the isolation feature 160 and across the fin isolation structures 150 a, 150 b, and 150 c, in accordance with some embodiments. The dummy gate structures extend between the fin structure 101 and the fin isolation structures 150 a, 150 b, and 150 c. Each dummy gate structure may include a dummy gate insulating layer and a dummy gate electrode layer over the dummy gate insulating layer.

Gate spacer layers 171 are formed on opposite sidewall surfaces of the corresponding dummy gate structure, in accordance with some embodiments. The gate spacer layers 171 may be made of silicon nitride, silicon oxide, silicon carbide, silicon oxynitride, or another applicable material.

Afterwards, a portion of the fin structure 101 that is exposed from the gate spacer layers 171 and the dummy gate structures is recessed, in accordance with some embodiments. In some embodiments, the fin structure 101 is recessed by an etching process, so that the top surface of the recessed fin structure 101 is lower than the top surface of the isolation feature 160. Afterwards, source/drain (S/D) features 175 are formed over the recessed fin structure 101 and protrude from the isolation feature 160, in accordance with some embodiments. In some embodiments, a strained material is grown over the recessed fin structure 101 by an epitaxial process to form the S/D features 175. The S/D features 175 are formed on opposing sidewall surfaces of the corresponding dummy gate structure. In some embodiments, the S/D features 175 include Ge, SiGe, InAs, InGaAs, InSb, GaAs, GaSb, InAlP, InP, or the like.

After the S/D features 175 are formed, an inter-layer dielectric (ILD) layer (not shown) is formed over the substrate 100, in accordance with some embodiments. In some embodiments, the ILD layer may include multilayers made of multiple dielectric materials, such as silicon oxide, silicon nitride, silicon oxynitride, tetraethoxysilane (TEOS), phosphosilicate glass (PSG), borophosphosilicate glass (BPSG), low-k dielectric material, and/or other applicable dielectric materials. The ILD layer may be formed by CVD, ALD, physical vapor deposition, (PVD), spin-on coating, or another applicable process. Afterwards, a planarization process, such as a CMP process, is performed on the ILD layer until the top surfaces of the dummy gate structures are exposed.

Afterwards, the dummy gate structures are removed and replaced by active gates structures 180, as shown in FIGS. 9 and 10 in accordance with some embodiments. FIG. 10 is a schematic cross-sectional view showing the semiconductor device structure taken along the line 10-10′ in FIG. 9. In some embodiments, the dummy gate structures are removed by an etching process, such as a dry etching process or a wet etching process.

Since the dummy gate structures are removed and replaced by the active gates structures 180, the active gates structures 180 are formed over the isolation feature 160 and across the fin isolation structures 150 a, 150 b, and 150 c, in accordance with some embodiments. The active gates structures 180 extend between the fin structure 101 and the fin isolation structures 150 a, 150 b, and 150 c. Similar to the dummy gate structure, each active gates structure 180 may include a gate insulating layer 173 and a gate electrode layer 170 over the gate insulating layer 173.

In some embodiments, the gate insulating layer 173 is made of a high k dielectric material, such as metal oxide. Examples of the high-k dielectric material may include hafnium oxide (HfO₂), hafnium silicon oxide (HfSiO), hafnium tantalum oxide (HfTaO), hafnium titanium oxide (HfTiO), hafnium zirconium oxide (HfZrO), zirconium oxide, titanium oxide, aluminum oxide, or other applicable dielectric materials. In some embodiments, the gate insulating layer 173 may be formed by CVD, PVD, ALD, or another applicable process.

In some embodiments, the gate electrode layer 170 is made of tungsten (W). In some embodiments, the gate electrode layer 170 is formed by CVD, PECVD, HDPCVD, MOCVD, or another applicable process.

Many variations and/or modifications can be made to embodiments of the disclosure. FIGS. 11, 12, and 13 show perspective representations of various stages of forming a semiconductor device structure, in accordance with some embodiments of the disclosure. The stages shown in FIGS. 11, 12, and 13 are similar to those shown in FIGS. 1, 2, 3, 4, 5, 6, 7, 8, and 9. In some embodiments, the materials, formation methods, and/or benefits of the semiconductor device structure shown in FIGS. 1, 2, 3, 4, 5, 6, 7, 8, and 9 can also be applied in the embodiments illustrated in FIGS. 11, 12, and 13, and are therefore not repeated.

A structure similar to FIG. 6 is provided, as shown in FIG. 11 in accordance with some embodiments. Unlike the structure shown in FIG. 6, the structure shown in FIG. 11 further includes an intermediate capping layer 136 formed between the first capping layer 130 and the second capping layer 140 in accordance with some embodiments. In some embodiments, the intermediate capping layer 136 is formed over the first capping layer 130 above the fins 101 a, 101 b, 101 c, 101 d, and 101 e and the insulating layer 120 in the openings 110 a and 110 b and conformally lines the upper portion of the openings 130 a and 130 b (not shown and as indicated in FIG. 6), so as to form openings 136 a and 136 b corresponding to the openings 130 a and 130 b. In some embodiments, the intermediate capping layer 136 in those openings 136 a and 136 b has sidewall surfaces covered by the first capping layer 130. Moreover, the second insulating layer 120 provides a sufficient recess depth, so that the bottom of the opening 136 a is substantially level with or above the top surfaces 103 of the fins 101 a, 101 b, 101 c, 101 d, and 101 e.

In some embodiments, the second capping layer 140 is formed over the insulating layer 110 above the patterned second masking layer 104 and fills the openings 136 a and 136 b. As a result, the second capping layer 140 in the opening 136 a has sidewall surfaces and a bottom surface (i.e., the bottom 137 of the opening 136 a) that are covered by the intermediate capping layer 136, so that the insulating layer 110 between the fins 101 a and 101 b is separated from the second capping layer 140 by the first capping layer 130 and the intermediate capping layer 136.

In some embodiments, the first capping layer 130 is made of a nitrogen-containing material or carbon- and nitrogen-containing material. For example, the first capping layer 130 is made of SiN, SiON, SiCN, SiOCN, TiN, AlON or another applicable material. The first capping layer 130 may be deposited by an ALD process, a CVD process, or another applicable process. In some embodiments, the intermediate capping layer 136 is made of a material that is different from the material of the first capping layer 130. For example, the intermediate capping layer 136 is made of a nitrogen-free material that is different from that of the second capping layer 140. For example, the intermediate capping layer 136 is made of Si, SiC, SiOC, SiO, SiO₂, HfO_(x), ZrO₂, Al₂O₃, or another applicable material. The intermediate capping layer 136 may be deposited by a CVD process, a PECVD process, or another applicable process.

After the second capping layer 140 is formed, a polishing process that is the same as or similar to the polishing process shown in FIG. 7 is performed, as shown in FIG. 12 in accordance with some embodiments. As a result, the fins 101 a, 101 b, 101 c, 101 d, and 101 e are exposed and a dual capping structure covering the entire top surface 120 a (not shown and as indicated in FIG. 5) of the insulating layer 120 is formed. Unlike the dual capping structure shown in FIG. 7, the dual capping structure includes the first capping layer 130 and the intermediate capping layer 136 since the second capping layer 140 is entirely removed during the polishing process.

After the dual capping structure is formed, the remaining insulating liner 106 is further recessed by a method that is the same as or similar to the method shown in FIG. 8 in accordance with some embodiments, so as to form an isolation feature 160 and fin isolation structures 150 a, 150 b, and 150 c.

Afterwards, gate spacer layers 171 and active gates structures 180 are formed over the isolation feature 160 and across the fin isolation structures 150 a, 150 b, and 150 c by a method that is the same as or similar to the method shown in FIG. 9, as shown in FIG. 13 in accordance with some embodiments. The active gates structures 180 extend between the fin structure 101 and the fin isolation structures 150 a, 150 b, and 150 c. Each active gates structure 180 may include a gate insulating layer 173 and a gate electrode layer 170 over the gate insulating layer 173.

Embodiments of a semiconductor device structure and a method for forming the same are provided. The semiconductor device structure includes an isolation feature and a fin isolation structure formed between adjacent first and second fins that protrude from a substrate. The formation of the fin isolation structure includes forming a first insulating layer that covers the first and second fins and is partially embedded in the isolation feature. A second insulating layer and an overlying dual capping structure are formed over the first insulating layer between the first and second fins and have sidewall surfaces covered by the first insulating layer. This dual capping structure includes a top capping layer made of a nitrogen-free material to serve as a polishing (e.g., CMP) stop layer for exposure of the first and second fins. The top capping layer prevents the property of the polishing slurry from being changed, thereby ensuring that the polishing process can stop on the top surfaces of the first and second fins. As a result, the polishing endpoint detection can be controlled, and the fin loss problem can be mitigated or eliminated.

In some embodiments, a semiconductor device structure is provided. The semiconductor device structure includes a substrate having adjacent first and second fins protruding from the substrate. The semiconductor device structure also includes an isolation feature between and adjacent to the first and second fins, and a fin isolation structure between the first fin and the second fin. The fin isolation structure includes a first insulating layer partially embedded in the isolation feature, a second insulating layer having sidewall surfaces and a bottom surface that are covered by the first insulating layer. The fin isolation structure also includes a first capping layer covering the second insulating layer and having sidewall surfaces that are covered by the first insulating layer, and a second capping layer having sidewall surfaces and a bottom surface that are covered by the first capping layer.

In some embodiments, a semiconductor device structure is provided. The semiconductor device structure includes a substrate having a fin structure protruding from the substrate. The fin structure includes a first fin, a second fin adjacent to and spaced apart from the first fin by a first distance and a third fin adjacent to and spaced apart from the second fin by a second distance that is different from the first distance. The semiconductor device structure also includes an isolation feature between and adjacent to the first fin and the second fin, and between and adjacent to the second fin and the third fin. The semiconductor device structure also includes a first insulating layer partially embedded in the isolation feature between the first fin and the second fin and between the second fin and the third fin. The semiconductor device structure also includes a second insulating layer having sidewall surfaces and a bottom surface that are covered by the first insulating layer between the first fin and the second fin. The semiconductor device structure also includes a dual capping structure covering the second insulating layer and having a top surface that is substantially level with the top surface of the fin structure.

In some embodiments, a method for forming a semiconductor device structure is provided. The method includes patterning a substrate to form adjacent first and second fins and a first opening between the first and second fins. The method also includes forming an insulating liner to cover the first and second fins and the first opening. The method also includes forming a first insulating layer over the insulating liner to cover the first and second fins and the first opening and form a second opening between the first and second fins. The method also includes filling a lower portion of the second opening with a second insulating layer. The method also includes forming a first capping layer over the first insulating layer and the second insulating layer to cover the first and second fins and an upper portion of the second opening and form a third opening between the first and second fins. The bottom of the third opening is lower than top surfaces of the first and second fins. The method also includes forming a second capping layer over the first capping layer to cover the first and second fins and fill the third opening. The method also includes successively polishing the second capping layer, the first capping layer, the first insulating layer, and the insulating liner until the first and second fins are exposed. The method also includes recessing the insulating liner after the polishing, so as to form an isolation feature.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

What is claimed is:
 1. A semiconductor device structure, comprising: a substrate having adjacent first and second fins protruding from the substrate; an isolation feature between and adjacent to the first fin and the second fin; and a fin isolation structure between the first fin and the second fin, comprising: a first insulating layer partially embedded in the isolation feature; a second insulating layer having sidewall surfaces and a bottom surface that are covered by the first insulating layer; a first capping layer covering the second insulating layer and having sidewall surfaces that are covered by the first insulating layer; and a second capping layer having sidewall surfaces and a bottom surface that are covered by the first capping layer.
 2. The semiconductor device structure as claimed in claim 1, further comprising a gate structure over the isolation feature and across the first fin and second fins and the fin isolation structure.
 3. The semiconductor device structure as claimed in claim 2, wherein the gate structure extends between the fin isolation structure and the first and second fins.
 4. The semiconductor device structure as claimed in claim 1, wherein the bottom surface of the second capping layer is below top surfaces of the first and second fins.
 5. The semiconductor device structure as claimed in claim 1, wherein the second capping layer has a top surface that is substantially level with top surfaces of the first and second fins.
 6. The semiconductor device structure as claimed in claim 1, wherein the first capping layer is made of a nitrogen-containing material, and the second capping layer is made of a nitrogen-free material.
 7. The semiconductor device structure as claimed in claim 1, wherein the first insulating layer is made of a nitrogen-containing material.
 8. A semiconductor device structure, comprising: a substrate having a fin structure protruding from the substrate, wherein the fin structure comprises a first fin, a second fin adjacent to and spaced apart from the first fin by a first distance and a third fin adjacent to and spaced apart from the second fin by a second distance that is different from the first distance; an isolation feature between and adjacent to the first fin and the second fin, and between and adjacent to the second fin and the third fin; a first insulating layer partially embedded in the isolation feature between the first fin and the second fin and between the second fin and the third fin; a second insulating layer having sidewall surfaces and a bottom surface that are covered by the first insulating layer between the first fin and the second fin; and a dual capping structure covering the second insulating layer and having a top surface that is substantially level with the top surface of the fin structure.
 9. The semiconductor device structure as claimed in claim 8, wherein the dual capping structure comprises: a nitrogen-free material layer over the second insulating layer; and a nitrogen-containing material layer between the second insulating layer and the nitrogen-free material layer.
 10. The semiconductor device structure as claimed in claim 9, wherein the first insulating layer between the first fin and the second fin is separated from the nitrogen-free material layer by the nitrogen-containing material layer.
 11. The semiconductor device structure as claimed in claim 9, wherein the nitrogen-free material layer is made of Si, SiC, SiOC, SiO, SiO₂, HfO_(x), ZrO₂, or Al₂O₃.
 12. The semiconductor device structure as claimed in claim 9, wherein the nitrogen-containing material layer is made of SiN, SiON, SiCN, SiOCN, TiN, or AlON.
 13. The semiconductor device structure as claimed in claim 8, further comprising a gate structure over the isolation feature and across the fin structure, the first insulating layer, and the dual capping structure.
 14. The semiconductor device structure as claimed in claim 13, wherein the gate structure extends between the fin structure and the first insulating layer.
 15. The semiconductor device structure as claimed in claim 8, wherein the first distance is greater than the second distance.
 16. A method of forming a semiconductor device structure, comprising: patterning a substrate to form adjacent first and second fins and a first opening between the first and second fins; forming an insulating liner to cover the first and second fins and the first opening; forming a first insulating layer over the insulating liner to cover the first and second fins and the first opening and form a second opening between the first and second fins; filling a lower portion of the second opening with a second insulating layer; forming a first capping layer over the first insulating layer and the second insulating layer to cover the first and second fins and an upper portion of the second opening and form a third opening between the first and second fins, wherein the bottom of the third opening is lower than top surfaces of the first and second fins; forming a second capping layer over the first capping layer to cover the first and second fins and fill the third opening; successively polishing the second capping layer, the first capping layer, the first insulating layer, and the insulating liner until the first and second fins are exposed; and recessing the insulating liner after the polishing, so as to form an isolation feature.
 17. The method as claimed in claim 16, wherein a portion of the first capping layer remains in the second opening and a portion of the second capping layer remains in the third opening after the polishing, so as to form a dual capping structure to cover the second insulating layer.
 18. The method as claimed in claim 17, further comprising forming a gate structure over the isolation feature and across the first and second fins and the dual capping structure, wherein the gate structure extends between the dual capping structure and the first and second fins.
 19. The method as claimed in claim 16, wherein a polishing selectivity of the second capping layer to the first and second fins is greater than that of the first capping layer to the first and second fins.
 20. The method as claimed in claim 16, wherein the first capping layer is made of a nitrogen-containing material, and the second capping layer is made of a nitrogen-free material. 